Process for producing renewable jet fuel compositions

ABSTRACT

Processes for producing jet fuel are disclosed. In one embodiment, syngas is converted to methanol, and a first portion of the methanol is converted to olefins using a methanol-to-olefins catalyst. The olefins are then oligomerized under conditions that provide olefins in the jet fuel range. The olefins can then optionally be isomerized and/or hydrotreated. A second portion of the methanol is converted to dimethyl ether, which is then reacted over a catalyst to form jet fuel-range hydrocarbons and aromatics. All or part of the two separate product streams can be combined, to provide jet fuel components which include isoparaffins and aromatics in the jet fuel range. The syngas is preferably derived from biomass or another renewable carbon-containing feedstock, thereby providing a biorefining process for the production of renewable jet fuel. In another embodiment, the process starts with methanol, rather than producing the methanol from syngas.

This application claims priority of U.S. provisional application No.61/667,605 filed on Jul. 3, 2012. All applications are included hereinin its entirety by reference.

FIELD OF THE INVENTION

The present invention generally relates to processes for the conversionof synthesis gas into renewable liquid fuels, including gasoline.

BACKGROUND OF THE INVENTION

Synthesis gas, which is also known as syngas, is a mixture of gasescomprising carbon monoxide (CO) and hydrogen (H₂). Generally, syngas maybe produced from any carbonaceous material. In particular, biomass suchas agricultural wastes, forest products, grasses, and other cellulosicmaterial may be converted to syngas.

Syngas is a platform intermediate in the chemical and biorefiningindustries and has a vast number of uses. Syngas can be converted intoalkanes, olefins, oxygenates, and alcohols such as ethanol. Thesechemicals can be blended into, or used directly as, diesel fuel,gasoline, and other liquid fuels. Syngas can also be directly combustedto produce heat and power. The substitution of alcohols and/orderivatives of alcohols in place of petroleum-based fuels and fueladditives can be particularly environmentally friendly when the alcoholsare produced from feed materials other than fossil fuels.

In recent years, considerable research has been devoted to providingalternative sources and manufacturing routes for jet fuels inrecognition of the fact that petroleum is a non-renewable resource andthat petroleum-based fuels such as gasoline and distillate willultimately become more expensive.

A major development within the chemical/petroleum industry has been thediscovery of the special catalytic capabilities of a family of zeolitecatalyst based upon medium-pore size shape selective metallosilicates.Discoveries have been made leading to a series of analogous processesdrawn from the catalytic capability of zeolites. Depending upon variousconditions of space velocity, temperature, and pressure, methanol can beconverted in the presence of zeolite-type catalysts to olefins which canoligomerize to provide gasoline or distillate, or can be convertedfurther to produce aromatics.

It has been demonstrated that alcohols, ethers, and carbonyl-containingcompounds can be converted to higher hydrocarbons, particularlyaromatics-rich high-octane gasoline, by catalytic conversion employing ashape-selective medium pore acidic zeolite catalyst such as H-ZSM-5.This conversion is described in, among others, U.S. Pat. Nos. 3,894,103;3,894,104; 3,894,106; 3,907,915; 3,911,041; 3,928,483; and, 3,969,426.The conversion of methanol to gasoline in accordance with thistechnology (the “MTG” process) produces mainly C₅₊ gasoline-rangehydrocarbon products together with C₃-C₄ gases and C₉ heavy aromatics.The desirable C₆-C₈ aromatics (principally benzene, toluene and xylenes)can be recovered as a separate product slate by conventionaldistillation and extraction techniques.

Traditional approaches for converting syngas to gasoline involve atwo-step process comprising converting syngas to methanol followed byconverting methanol to gasoline. What are needed, in view of the art andcommercial drivers, are process configurations, apparatus, and suitablecatalysts for conversion of syngas into gasoline components as well asoxygenates, such as alcohols, for blending into oxygenated gasoline.Additionally, methods that proceed through higher alcohols (ethanol andheavier) are desired in order to take advantage of the state of the artfor ethanol synthesis and higher-alcohol synthesis from syngas.

SUMMARY OF THE INVENTION

In one embodiment, the present invention relates to a process forproducing jet fuel components. The process comprises:

(a) generating or providing syngas;

(b) converting the syngas to methanol;

(c) converting at least some of the methanol to olefins, primarilyethylene and propylene, with some amount of butylene and higher olefins,

(d) converting at least some of the methanol to dimethyl ether,

e) converting the dimethyl ether to one or more jet fuel rangehydrocarbons and aromatics using a zeolite catalyst,

f) oligomerizing the ethylene and propylene, and, optionally, the higherolefins, to produce olefins in the jet fuel range,

h) optionally isomerizing and/or hydrogenating the olefins in the jetfuel range to form paraffins in the jet fuel range, and

combining one or more products from step e) with one or more of theproducts of step h).

The syngas can be derived, for example, from biomass such as wood chipsor from any other carbon-containing feedstock.

The jet fuel components are not particularly limited but can include atleast one C₅₋₁₀ hydrocarbon. Jet fuel components can include branchedhydrocarbons, olefins, and aromatics.

Certain methods of the invention further include hydrotreating,isomerizing, or otherwise catalytically treating at least some of thejet fuel components.

The jet fuel components can be used directly as jet fuel, or blendedwith another fuel to generate commercial jet fuel.

In another embodiment, the invention relates to jet fuel compositions.In one aspect of this embodiment, a composition comprises the jet fuelcomponents produced in accordance with any of the methods describedherein. In some embodiments, a composition consists essentially of thejet fuel components produced in accordance with any of the methodsdescribed herein. In other embodiments, the jet fuel compositionscomprise one or more conventional jet fuel compositions, such as JP8,JetA, JP1, and the like, to which one or more of the components producedaccording to the methods described herein are added.

These and other embodiments, features, and advantages of the presentinvention will become more apparent to those skilled in the art whentaken with reference to the following detailed description of theinvention in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a block-flow diagram depicting an exemplary process forconversion of syngas to methanol, separation of the methanol into tostreams, conversion of a first portion of the methanol into paraffinsand aromatics, conversion of a second portion of the methanol intoethylene, propylene and other olefins, conversion of the ethylene andpropylene and, optionally, higher olefins into oligomers, and optionalisomerization and/or hydrotreatment of the oligomers, according to someembodiments of the invention.

DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION

Certain embodiments of the present invention will now be furtherdescribed in more detail, in a manner that enables the claimed inventionso that a person of ordinary skill in this art can make and use thepresent invention.

Unless otherwise indicated, all numbers expressing reaction conditions,stoichiometries, concentrations of components, and so forth used in thespecification and claims are to be understood as being modified in allinstances by the term “about.” Accordingly, unless indicated to thecontrary, the numerical parameters set forth in the followingspecification and attached claims are approximations that may varydepending at least upon the specific analytical technique. Any numericalvalue inherently contains certain errors necessarily resulting from thestandard deviation found in its respective testing measurements.

As used in this specification and the appended claims, the singularforms “a,” “an,” and “the” include plural referents unless the contextclearly indicates otherwise. Unless defined otherwise, all technical andscientific terms used herein have the same meaning as is commonlyunderstood by one of ordinary skill in the art to which this inventionbelongs. If a definition set forth in this section is contrary to orotherwise inconsistent with a definition set forth in patents, publishedpatent applications, and other publications that are herein incorporatedby reference, the definition set forth in this specification prevailsover the definition that is incorporated herein by reference.

Variations of this invention are premised, at least in part, on theconversion of syngas into methanol, ethanol, and, optionally, one ormore higher alcohols. A “higher alcohol,” as used herein, means a C₃,C₄, C₅, or higher alcohol, but the majority of higher alcohols are C₃₋₅,more predominantly, C₃₋₄ alcohols.

Jet fuel components include any molecule capable of being combusted in ajet fuel engine to provide power for an airplane or other machineburning jet fuel for energy. Jet fuel components include alkanes,olefins, cyclic hydrocarbons, and aromatics.

Some variations of the invention relate to an integrated biorefinerycapable of producing one or more liquid transportation fuels, includingoxygenated fuels. In some embodiments, the invention provides a processthat converts syngas into jet fuel components. In some embodiments, theinvention provides a process that converts syngas into methanol, andconverts at least a portion of the methanol to dimethyl ether (DME),which is then chemically converted into jet fuel components, andconverts at least another portion of the methanol to olefins, which arethen oligomerized, and, optionally but preferably, isomerized and/orhydrotreated, and products in the jet fuel range are then isolated. Theproduct streams from the conversion of dimethyl ether and the olefinoligomerization, and optional isomerization and hydrotreatment streams,can be combined. The combined products streams comprise aromatics andhydrocarbons in the C₅₋₁₅ range, and can be used as jet fuel. Dependingon the desired fuel composition, the amounts of the separate productstreams that are to be combined can be varied, for example, to providemore C₅₋₉ hydrocarbons and aromatics, or more C₁₀₋₁₄ or C₁₀₋₁₆ products.It is believed that no other process offers this much flexibility infine-tuning jet fuel production, particularly in those embodiments wherebiomass is used as a feedstock to produce jet fuel.

In some variations, syngas is produced or otherwise provided in abiorefinery. The syngas can be divided into a plurality of streams andfed to several unit operations. Biorefinery optimization can be carriedout to adjust the splits to the different units, for economic reasons.Syngas can be a fuel itself to provide internal process energy, or solddirectly as a co-product, or converted into electricity for externalsale. At least a portion of the syngas, in the context of the presentinvention, is converted to liquid fuels.

Engineering optimization can be conducted to achieve energy integration.For example, energy requirements for product separations can be reducedby combining portions of the product streams from individual processesinto a single unit, such as distillation and drying. Various levels ofheat recovery can be employed to meet drying and separationrequirements.

In one embodiment, the process does not start with syngas generation,but rather, starts with methanol produced at a separate facility. Thatis, methanol can be obtained as a feedstock, and a portion of themethanol converted to dimethyl ether, and subsequently converted to jetfuel range components, and a portion of the methanol can be converted toolefins, and the olefins subjected to olefin oligomerization, and,optionally, one or more of isomerization and hydrotreatment steps.

Also, specifications on intermediate streams can be relaxed to reduceenergy requirements. In some embodiments, individual methanol streamsare partially or completely dried for feeding into an alcohols-to-jetfuel step, thereby reducing drying requirements and costs. In someembodiments, a methanol stream is allowed to contain ethanol in excessof that described in an ASTM specification, such as 1-2 vol %, forfeeding to a methanol-to-dimethyl ether step, thereby reducing energycosts. In some embodiments, ethanol and higher alcohols are fed to analcohol dehydration step.

Various embodiments of the invention produce one or more jet fuelcomponents selected from the group consisting of 2-methylbutane,4-methylpentene, methylcyclopentane, benzene, toluene, ethylbenzene,m-xylene, p-xylene, o-xylene, 1-ethyl-4-methylbenzene,1,2,4-trimethylbenzene, 1-methyl-4-(ethylmethyl)-benzene,1,2-diethylbenzene, 1-ethyl-2,4-dimethylbenzene,2,3-dihydro-1-methyl-1-indene, naphthalene, 2-methylnaphthalene,1,8-dimethylnaphthalene, 2-(1-methylethyl)- and naphthalene. Otheralkanes, olefins, cyclic hydrocarbons, and aromatics can be produced.

Also, in some embodiments, light components (such as methane, ethane,and propane) may be recovered as fuel gas suitable for energyrequirements within the biorefinery. In certain embodiments, crude jetfuel components may be distilled to produce a fuel-grade LPG-type streamand a jet fuel stream.

The present invention will now be further described by reference to thefigures. This exemplary detailed description illustrates by way ofexample, not by way of limitation, the principles of the invention.

In FIG. 1, a process block-flow diagram is depicted for variousprocesses of the invention.

FIG. 1 is a block-flow diagram depicting an exemplary process forconversion of syngas to methanol, conversion of a portion of themethanol to dimethyl ether, and conversion of a portion of the methanolto olefins, and subsequent oligomerization of the olefins to produceolefins in the jet fuel range, which can then optionally be isomerizedand/or hydrotreated, according to some embodiments of the invention. Inthis variation, a starting syngas stream is provided (e.g., producedfrom biomass or otherwise received). The starting syngas stream isconverted to methanol. The methanol is then divided into at least twostreams, with a first stream converted to dimethyl ether, and thedimethyl ether is then converted to jet fuel range components, and asecond stream converted to olefins, which are subjected tooligomerization conditions. The oligomers, which can optionally beisomerized and/or hydrotreated, are then combined with some or all ofthe products produced by reaction of the dimethyl ether.

Zeolite and Molecular Sieve Catalysts

Several of the process steps described herein use zeolite or molecularsieve catalysts.

A “zeolite catalyst” as used herein includes molecular sieves and otherequivalent functional forms.

Zeolitic materials, both natural and synthetic, have been demonstratedin the past to have catalytic properties for various types ofhydrocarbon conversion. Certain zeolitic materials are ordered, porouscrystalline aluminosilicates having a definite crystalline structure asdetermined by X-ray diffraction, within which there are a large numberof smaller cavities which may be interconnected by a number of stillsmaller channels or pores. These cavities and pores are uniform in sizewithin a specific zeolitic material. These materials have come to beknown as “molecular sieves” and are utilized in a variety of ways totake advantage of these properties.

Molecular sieves, both natural and synthetic, include a wide variety ofpositive ion-containing crystalline silicates. These silicates can bedescribed as a rigid three-dimensional framework of SiO₄ and PeriodicTable Group IIIA element oxide, e.g., AlO₄, in which the tetrahedra arecross-linked by the sharing of oxygen atoms whereby the ratio of thetotal Group IIIA element, e.g., aluminum, and silicon atoms to oxygenatoms is 1:2. The electrovalence of the tetrahedra containing the GroupIIIA element, e.g., aluminum, is balanced by the inclusion in thecrystal of a cation, e.g., an alkali metal or an alkaline earth metalcation.

One type of cation may be exchanged either entirely or partially withanother type of cation utilizing ion-exchange techniques in aconventional manner. By means of such cation exchange, it has beenpossible to vary the properties of a given silicate by suitableselection of the cation. The spaces between the tetrahedra are occupiedby molecules of water prior to dehydration.

Prior art techniques have resulted in the formation of a great varietyof synthetic zeolites. Many of the zeolites have come to be designatedby letter or other convenient symbols, as illustrated by zeolite Z (U.S.Pat. No. 2,882,243); zeolite X (U.S. Pat. No. 2,882,244); zeolite Y(U.S. Pat. No. 3,130,007); zeolite ZK-5 (U.S. Pat. No. 3,247,195);zeolite ZK-4 (U.S. Pat. No. 3,314,752); zeolite ZSM-5 (U.S. Pat. No.3,702,886); zeolite ZSM-11 (U.S. Pat. No. 3,709,979); zeolite ZSM-12(U.S. Pat. No. 3,832,449), zeolite ZS-20 (U.S. Pat. No. 3,972,983);zeolite ZSM-35 (U.S. Pat. No. 4,016,245); and zeolite ZSM-23 (U.S. Pat.No. 4,076,842), for example.

The SiO₂/Al₂O₃ ratio of a given zeolite is variable. For example,zeolite X can be synthesized with SiO₂/Al₂O₃ ratios of from 2 to 3;zeolite Y, from 3 to about 6. In some zeolites, the upper limit of theSiO₂/Al₂O₃ ratio is unbounded. ZSM-5 is one such example wherein theSiO₂/Al₂O₃ ratio is at least 5 and up to the limits of presentanalytical measurement techniques.

Syngas Production

The syngas can be produced from biomass, but that is not necessary forthis invention. Other sources of syngas include, for example, naturalgas, coal, crude oil, and any other carbonaceous material.

In some embodiments, the syngas provided or generated for methods ofthis invention is produced from one or more carbon-containing feedstocksselected from timber harvesting residues, softwood chips, hardwoodchips, tree branches, tree stumps, leaves, bark, sawdust, paper pulp,corn stover, wheat straw, rice straw, sugarcane bagasse, switchgrass,miscanthus, animal manure, municipal solid waste, municipal sewage,commercial waste, used tires, grape pumice, almond shells, pecan shells,coconut shells, coffee grounds, grass pellets, hay pellets, woodpellets, cardboard, paper, plastic, rubber, cloth, coal, lignite, coke,lignin, and/or petroleum. Mixtures of any of these feedstocks can beused.

Syngas can be produced by any known means, such as by one or more ofgasification, pyrolysis, devolatilization, steam reforming, and partialoxidation of one or more feedstocks recited herein.

The syngas-generation unit or step may be a gasifier, such as afluidized-bed gasifier. In variations, the gasifier type may beentrained-flow slagging, entrained flow non-slagging, transport,bubbling fluidized bed, circulating fluidized bed, or fixed bed. Someembodiments employ known gasification catalysts. “Gasification” and“devolatilization” generally refer herein to the reactive generation ofa mixture of at least CO, CO₂, and H₂, using oxygen, air, and/or steamas the oxidant(s).

In some embodiments, syngas is produced by the methods taught in U.S.patent application Ser. No. 12/166,167, entitled “METHODS AND APPARATUSFOR PRODUCING SYNGAS,” filed Jul. 1, 2008.

Gasification is known as the art to convert a variety of feedstocks,such as coal, methane, methanol, ethanol, glycerol, biomass such as cornstover, switchgrass, sugar cane bagasse, sawdust, and the like, blackliquor, municipal solid waste, and lignin to synthesis gas. Manygasifiers have been developed, and one exemplary gasifier is that soldby TCG Energy (www.tcgenergy.com). Another gasifier of noteable mentionis the Thermoselect (www.iwtonline.com). Also, see, for example,[http://www.biocap.ca/files/biodiesel/dalai.pdf]. The Wiley gasifier,covered by one or more of U.S. Pat. Nos. 7,638,070; 7,857,995;7,968,006; 8,017,040; 8,017,041 and 8,021,577 can also be used.

The water-gas-shift reaction plays an important role in the conversionof certain of these feedstocks to hydrogen via steam gasification andpyrolysis. Catalytic steam gasification can give high yields of syngasat relatively low temperatures. Biomass can be converted to syngas usinga variety of known methods, including thermal gasification, thermalpyrolysis and steam reforming, and/or hydrogasification each of whichcan produce syngas yields of 70-75% or more.

These approaches are well known in the art, and need not be described inmore detail Gasification of coal was used in England and in the UnitedStates to produce “town gas” to light the city streets over a hundredyears ago. The German war effort was fueled by coal gasification duringWorld War II. Currently over 40% of South African motor fuel is derivedfrom coal gasification, as well as 100% of their aviation fuel. Majorsuppliers of gasification technology include Sasol Lurgi, GE,Conoco-Phillips, and Shell with dozens of large, expensive plantsoperating worldwide.

In the U.S. a large gasification plant is producing synthetic naturalgas in North Dakota, and two integrated combined cycle (IGCC)demonstration plants are generating electricity—one in Florida and theother in Indiana. Eastman Chemical's coal gasification plant located inTennessee once produced all Kodak film for the photography industry. Ithas operated successfully for over 25 years and continues to producemethanol, plastics, and other products for the chemical industry.Gasification is accomplished with heat, pressure, and the injection ofionized water.

The basic chemical reaction used in gasification is C+H2O=CO+H2. Thisprocess begins in a heated, oxygen-starved environment (known as thepyrolysis chamber), which drives off moisture and volatile gasescontained in the feedstock. Pyrolysis produces carbon char and ash thatmoves into a separate, externally heated gasification reactor, whichconverts the solid carbon molecule into a gaseous state. Next, in TCG'sprocessionized water is injected in a process known as steam reformationto create a water shift reaction to produce Syngas. The hot Syngas iswater quenched and cleansed of its impurities in a proprietary, ionizedwater treatment system, thus delivering a clean, dry Syngas with noliquid discharge from the plant operation. It is important to note thatthe TCG process is not a typical gasification process, which requiresthe injection of oxygen for the reaction: 2C+O2++H2O=CO+H2+CO2, nor isit heated by internal feedstock combustion which is represented byC+O2=CO2. Conventional gasification plants produce high amounts ofcarbon dioxide in their internal combustion processes. The externallyheated TCG process actually reduces CO2 through the following reaction:CO2+C=2CO and does not produce harmful combustion by-products. The othergasifier that has received some merit is the Thermochem gasifier thatuses a pulse system to make syngas, which leaves many others to make thesyngas in the correct ratio to produce various chemicals and fuels.

Syngas Cleanup

Syngas is converted to methanol by contact with a suitable catalystunder reactive conditions. Depending on the quality of the syngas, itmay be desirable to purify the syngas prior to the methanol-generatingreactor to remove carbon dioxide produced during the syngas reaction,and any sulfur compounds, if they have not already been removed. Thiscan be accomplished by contacting the syngas with a mildly alkalinesolution (e.g., aqueous potassium carbonate) in a packed column. Thisprocess can also be used to remove carbon dioxide from the productstream.

One example of a suitable syngas cleanup process is called extractiveMerox. Merox is an acronym for mercaptan oxidation. It is a proprietarycatalytic chemical process developed by UOP, and used in oil refineriesand natural gas processing plants to remove mercaptans from a variety ofproducts, including syngas, LPG, propane, butanes, light naphthas,kerosene and jet fuel by converting them to liquid hydrocarbondisulfides.

The Merox process requires an alkaline environment which, in some of theprocess versions, is provided by an aqueous solution of sodium hydroxide(NaOH), a strong base, commonly referred to as caustic. In otherversions of the process, the alkalinity is provided by ammonia, which isa weak base.

The overall chemical reaction can be generalized as follows:4RSH+O2→2RSSR+2H2O

The catalyst in some versions of the process is a water-soluble liquid,such as methanol. In other versions, the catalyst is impregnated ontocharcoal granules.

The Merox process is usually more economical than using a catalytichydrodesulfurization process for much the same purpose, though thelatter can be used if desired.

Water-Gas Shift Chemistry

Biomass gasification typically produces a synthesis gas with anapproximately 1/1 ratio of hydrogen to carbon monoxide. It is generallydesirable to have a 2/1 ratio of hydrogen to carbon monoxide whencarrying out methanol synthesis. Accordingly, it is important toincrease the amount of hydrogen in the syngas. This is typically doneusing water-gas shift chemistry, which involves reacting water withcarbon monoxide to produce hydrogen and carbon dioxide. The generalreaction is shown below:CO+H₂O→CO₂+H₂

Syngas Conversion to Methanol

In 1923, the German chemists Alwin Mittasch and Mathias Pier developed ameans to convert synthesis gas into methanol. This technology isdescribed in U.S. Pat. No. 1,569,775, and the process used a chromiumand manganese oxide catalyst, and required extremely vigorousconditions—pressures ranging from 50 to 220 atm, and temperatures up to450° C.

Modern methanol production is more efficient through the use ofcatalysts (commonly copper) capable of operating at lower pressures. Themodern low pressure methanol (LPM) process was developed by ICI in thelate 1960s with the technology now owned by Johnson Matthey.

The carbon monoxide and hydrogen then react on a second catalyst toproduce methanol. Today, the most widely used catalyst is a mixture ofcopper, zinc oxide, and alumina first used by ICI in 1966. At 5-10 MPa(50-100 atm) and 250° C., it can catalyze the production of methanolfrom carbon monoxide and hydrogen with high selectivity:CO+2H₂→CH₃OH

Representative catalysts and conditions are described, for example, inVanden Bussche and Froment, 1996 “A steady-state kinetic model formethanol synthesis and the water gas shift reaction on a commercialCu/ZnO/Al2O3 catalyst,” Journal of Catalysis, 161, pp. 1-10.

It is worth noting that the production of synthesis gas from methaneproduces three moles of hydrogen gas for every mole of carbon monoxide,while the methanol synthesis consumes only two moles of hydrogen gas permole of carbon monoxide. One way of dealing with the excess hydrogen isto inject carbon dioxide into the methanol synthesis reactor, where it,too, reacts to form methanol according to the equation:CO₂+3H₂→CH₃OH+H₂O

Mature technologies available for biomass gasification are being usedfor methanol production. For instance, woody biomass can be gasified towater gas (a hydrogen-rich syngas), by introducing a blast of steam in ablast furnace. The water-gas/syngas can then be synthesized to methanolusing standard methods. The net process is carbon neutral, since the CO₂byproduct is required to produce biomass via photosynthesis. The overallchemical process is summarized below:2C₁₆H₂₃O₁₁+19H₂O+O₂→42H₂+21CO+11CO₂→21CH₃OH+11CO₂

This process is extremely advantageous, in that it 21 of the 32 carbonatoms present in the starting material are converted to methanol, andonly 11 of the 32 carbon atoms are converted to carbon dioxide.

Conversion of Methanol to Dimethyl Ether

Dimethyl ether (DME), also known as methoxymethane, is the organiccompound with the formula CH₃OCH₃. It is a colorless gas that is used asa precursor to gasoline-range hydrocarbons using the process describedherein, though DME can act as a clean fuel when burned in enginesproperly optimized for DME, such as diesel engines.

After synthesis gas is converted into methanol as described above,subsequent methanol dehydration in the presence of a different catalyst(for example, silica-alumina) produces DME. As described, this is atwo-step (indirect synthesis) process that starts with methanolsynthesis and ends with DME synthesis (methanol dehydration). Ideally,this process is conducted using organic waste or biomass.

This process has been conducted at commercial scale (see, for example,Manfred Müller, Ute Hübsch, “Dimethyl Ether” in Ullmann's Encyclopediaof Industrial Chemistry, Wiley-VCH, Weinheim, 2005).

Alternatively, in one embodiment, DME is produced through directsynthesis, using a dual catalyst system that permits both methanolsynthesis and dehydration in the same process unit, with no methanolisolation and purification (see, for example, P. S. Sai Prasad et al.,Fuel Processing Technology, 2008, 89, 1281). In this embodiment, byeliminating the intermediate methanol synthesis stage, the processprovides efficiency advantages and cost benefits relative to where themethanol is isolated.

In one embodiment, the catalysts and conditions are those described inU.S. Pat. No. 65,908,963 by Voss, Joensen, and Hansen, entitled“Preparation of fuel grade dimethyl ether” or Sofianos and Scurrell,1991, “Conversion of synthesis gas to dimethyl ether over bifunctionalcatalytic systems,” Ind. Eng. Chem. Res., 30 (11), pp. 2372-2378.

Both the one-step and two-step processes above are commerciallyavailable. Currently, there is more widespread application of thetwo-step process since it is relatively simple and start-up costs arerelatively low.

Conversion of Dimethyl Ether to Jet Fuel Components

The DME produced as described above is then further dehydrated over azeolite catalyst, such as ZSM-5, to give a jet fuel-range hydrocarbonswith 80% (by weight based on the organics in the product stream) C₅₊hydrocarbon products.

The catalyst, such as ZSM-5, is frequently deactivated by a carbonbuild-up (“coking”) over time in converting methanol to gasoline. Thecatalyst can be re-activated by burning off the coke in a stream of hot(500° C. (930° F.)) air. However, the number of re-activation cycles islimited.

Representative catalysts and conditions are described, for example, inKolesnichenko et al., “Synthesis of gasoline from syngas via dimethylether,” Kinetics and Catalysis Volume 48, Number 6, 789-793, 2007, alsopublished in Kinetika i Kataliz, 2007, Vol. 48, No. 6, pp. 846-850 bythe same authors.

In this embodiment, Zeolite H-TsVM is loaded with palladium by differentmethods. The properties of the resulting catalysts in gasoline synthesisfrom syngas via dimethyl ether depend on the way in which palladium wasintroduced. The catalysts have been characterized by ammoniatemperature-programmed desorption (TPD), temperature-programmed reactionwith hydrogen, and X-ray photoelectron spectroscopy. According toammonia TPD data, use of a palladium amine complex instead of palladiumchloride reduces the concentration of strong acid sites and raises theconcentration of medium-strength acid sites, thereby reducing the yieldof C₁₋₄ hydrocarbons and increasing the yield of hydrocarbons in the jetfuel range. At T=340° C., P=100 atm, and GHSV=2000 h-1, the dimethylether conversion is 98-99%, the selectivity for hydrocarbons in the jetfuel range is >60%, the isoparaffin content of the product is ˜61%, andthe arene content is not higher than 29%.

Additional catalysts and conditions are described in U.S. Pat. No.4,011,275 by Zahner, entitled “Conversion of modified synthesis gas tooxygenated organic chemicals,” and U.S. Pat. No. 4,098,809 by Pagani,entitled “Process for the production of dimethyl ether.”

Additional catalysts are well known to those of skill in the art, andthe process described herein is not limited to the catalystsspecifically mentioned herein.

Conversion of Methanol to Olefins

A portion of the methanol stream produced from syngas (or another sourceof methanol) can be passed over a methanol-to-olefin catalyst togenerate a mixture of ethylene and propylene, optionally with a minoramount of butylene and higher olefins. Any suitable methanol-to-olefincatalyst can be employed. That is, any material exhibiting activity forconverting methanol to one or more olefins can be employed.

In some embodiments, the methanol-to-olefin catalyst comprises analuminosilicate zeolite, such as one selected from the group consistingof ZSM-5, ZSM11, ZSM-12, ZSM-23, ZSM-35, and ZSM-48.

In some embodiments, the methanol-to-olefin catalyst comprises asilicoaluminophosphate (“SAPO”), such as a SAPO selected from the groupconsisting of SAPO-5, SAPO-8, SAPO-11, SAPO-16, SAPO-17, SAPO-18,SAPO-20, SAPO-31, SAPO-34, SAPO-35, SAPO-36, SAPO-37, SAPO-40, SAPO-41,SAPO-42, SAPO-44, SAPO-47, and SAPO-56.

SAPOs can be synthesized by forming a mixture containing sources ofsilicon, aluminum, and phosphorus mixed with an organic template, andthen crystallizing the molecular sieve at reaction conditions. Manyfactors affect the form the molecular sieve takes, including therelative amounts of the different components, the order of mixing, thereaction conditions (e.g. temperature and pressure) and the choice oforganic template.

A preferred methanol-to-olefin catalyst that can be used is SAPO-34(also referred to herein as H-SAPO-34). The preparation of SAPO-34 isknown in the art, as exemplified in U.S. Pat. No. 4,440,871, issued toUnion Carbide on Apr. 3, 1984, which is incorporated by reference hereinin its entirety. SAPO-34 has a three-dimensional microporous crystalframework structure and an empirical composition on an anhydrous basisof (Si_(x)Al_(y)P_(z))O₂ where x, y and z represent the mole fractionsof silicon, aluminum, and phosphorus, respectively, and where typicallyx+y+z=1.

Without being limited by any hypothesis, it is believed that theframework structure can trap organic intermediates (such asethylbenzenes) deriving from methanol.

These organic intermediates act as organic reaction centers thatcatalyze the olefin-forming reactions in cooperation with active sitesover the surface of the catalyst. Olefins, such as ethylene andpropylene, are small enough to exit the micropores of SAPO-34.

SAPO-34 offers a good combination of catalyst activity, selectivity, anddurability. Ethylene/propylene ratios in H-SAPO-34 may be driven byincreased temperatures; at higher temperatures ethylene selectivitiesincrease. At higher temperatures, coking rates are higher so morefrequent regeneration is typically needed.

It can be further beneficial for the methanol-to-olefin catalyst toemploy silicoaluminophosphates that also include at least one transitionmetal. Preferably, the transition metal is selected from manganese,nickel, or cobalt. The process of incorporating the transition metal maybe accomplished through any one of the standard methods well known tothose skilled in the art. In one embodiment, a solution of the desiredmetal is first made by dissolving the desired amount of themetal-containing compound in water under mild conditions. Thetemperature of mixing is dependent upon the solubility of the metalcompound in water, or another medium.

The amount of metal which is incorporated may vary over a wide rangedepending, at least in part, on the selected silicoaluminophosphate (orother material) and on the incorporation method. The amount of metalincorporated is measured on an atomic metal basis in terms ofsilicon-to-metal ratio. The silicon-to-metal atomic ratios are in therange from about 0.1:1 to about 1000:1, preferably from about 1:1 toabout 500:1, and most preferably from about 10:1 to about 200:1.

In some embodiments wherein nickel is the selected transition metal,high methanol-to-olefin conversion can be accomplished by usingNi-SAPO-34. For example, use of Ni-SAPO-34 is described in Inui andKang, “Reliable procedure for the synthesis of Ni-SAPO-34 as a highlyselective catalyst for methanol to ethylene conversion,” AppliedCatalysis A: General, vol. 164, 211-223, 1997. As taught therein,ethylene selectivity is 88% over Ni-SAPO-34, at 425-450° C. and close toatmospheric pressure.

In some embodiments, ethylene is the preferred olefin. In otherembodiments, propylene is the preferred olefin. In some embodiments, itis preferred to product higher quantities of C₃₊ olefins, includingpropylene, butenes (e.g., 1-butene and 2-butene), and optionally higherolefins. Generally, process conditions and catalysts can be selected tooptimize selectivity to one particular olefin, which can be ethylene orpropylene in particular embodiments. Or, process conditions andcatalysts can be selected to optimize selectivity to total olefinsrather than non-olefins (e.g., alkanes, aromatics, and CO₂). Processconditions and catalysts can also be selected to maximize methanolconversion, maximize yield of total olefins, maximize yield of C₂-C₃olefins, or maximize yield of a specific olefin such as ethylene orpropylene.

Preferably, methanol is completely or nearly completely converted in theolefin-forming process step. In various embodiments, selectivities toethylene are in the 50-75 mol % range, while selectivities to propyleneare in the 25-50 mol % range. In preferred embodiments, negligiblequantities of methane and carbon dioxide are produced during olefinformation. Production of carbon dioxide can occur, however, in the gasphase away from catalyst surfaces, or possibly catalyzed by othernon-selective surfaces present, such as walls of the reactor.

The olefin-forming reaction is exothermic. The catalyst can producecoke, and if that occurs, the catalyst can be periodically regeneratedby hot air or oxygen. A plurality of reactors can be employed, so thatwhen one is being regenerated, the other reactors can continueoperation.

The temperature for the olefin-forming step(s) can be 375-425 C, forexample. Higher temperatures will generally lead to higher selectivityto ethylene relative to propylene, but the choice of catalyst will alsodictate product distribution. Any pressure can be employed, andselection of pressure will typically be dictated by economics andintegration with an overall process. Reactor configurations are furtherdiscussed below.

Oligomerization of Ethylene and Higher Olefins

There are several commercial processes which oligomerize ethylene tolinear alpha olefins, any of which can be used. Several of theseprocesses produce wide distributions of linear alpha olefins. These arethe Ethyl Corporation (Ineos) process, Gulf (Chevron Phillips ChemicalCompany), Shell Oil Company SHOP process, the Idemitsu Petrochemicalprocess and the SABIC-Linde α-Sablin process.

The α-Sablin process is a low-pressure ethylene oligomerization processconducted over heterogeneous catalyst in a slurry bed. The process alsomakes a C₄₋₂₀₊ distribution of alpha-olefins.

Phillips (CP Chemical Company) ethylene trimerization process producesonly 1-hexene. The IFP process dimerizes ethylene to high purity1-butene. Mixtures of ethylene and butene and/or hexene can be subjectedto further reactions, such as dimerization and/or trimerization, toproduce hydrocarbons in the jet fuel range.

While the Ethyl process makes a Pseudo-Poisson distribution of products,most others, including the Sasol process, make a Schultz-Florydistribution.

Ineos (Ethyl) Process

The Ineos process is commonly called stoichiometric Ziegler process. Itis a two-step process. In the first step, a stoichiometric quantity oftriethyl aluminum in olefin diluent is reacted with excess ethylene athigh pressure (above 1000 psig) and relatively low temperature (below400° F.). On the average, nine moles of ethylene are added per mole oftriethyl aluminum, resulting in, on average, a tri-octyl aluminum. Thedistribution of alkyl chains on the aluminum is determined bystatistical bell curve distribution except for some smearing to thelight side due to the kinetic phenomena and some smearing to the heavyside due to some incorporation of heavier olefins into the chain. Excessethylene and olefin diluent are flashed off. The heavy aluminumtri-alkyls are reacted with ethylene again in a displacement or atransalkylation reaction, but at high temperature (over 400° F.) and atlow pressure (less than 1000 psig) to recover triethyl aluminum and astatistical distribution of linear alpha olefins, which serve as theolefin diluent in the chain-growth step.

CP Chemicals (Gulf) Process

The Gulf linear alpha olefin process is commonly called a catalyticZiegler process. Triethyl aluminum is used as a catalyst, but incatalytic amounts and the process is a single-step process. Tri-ethylaluminum and excess ethylene are fed to a plug flow-reactor. Thereaction is conducted at high pressure and high temperature. Excessethylene is flashed off. The tri-ethyl aluminum catalyst is washed outof the product with caustic and the linear alpha olefins are separated.The product distribution is a Schultz-Flory distribution typical ofcatalytic processes.

In some embodiments, ethylene oligomerization yields olefins such as1-butene, 1-hexene and 1-octene. These olefins can be combined withethylene and subjected to olefin dimerization and/or trimerizationreactions to provide hydrocarbons in the jet fuel range.

C₈₋₁₆ linear alpha olefins are in the desired jet fuel range, and can besubjected to isomerization and/or hydrotreatment steps.

Higher molecular weight olefins can be subjected to hydrocracking toprovide additional material in the desired jet fuel range, or,alternatively, can be combined with lower molecular weight olefins andsubjected to molecular averaging conditions to arrive at additionalmaterial in the desired jet fuel range.

During oligomerization processes, in addition to diesel cut products,products belonging to the gasoline fraction (boiling point lower than180° C. and high octane number), can also be obtained.

During the oligomerization of olefins, the physical characteristics ofthe products obtained (cetane number, boiling point, viscosity, etc.)are greatly influenced by the branching degree of the products. If thecatalyst used is not selective, the branching becomes considerable,which can be desirable for use in producing jet fuel components, incontrast to diesel fuel, where the branching would undesirably lower thecetane number in the diesel fuel. In one embodiment, a selectivecatalyst is used, and in another embodiment, a less selective catalystis used.

One such selective zeolites is ZSM-5, and this zeolite is used in theMOGD process (Mobil Olefins to Gasoline and Distillate), as disclosed inU.S. Pat. No. 4,150,062 and U.S. Pat. No. 4,227,992. The productsobtained from the reaction of butenes are trimers and tetramers,characterized by a low branching degree. The gas oil fraction however islower than that of the jet fuel fraction. In order to provide butenes asfeedstocks to this process, the ethylene can first be subjected to anolefin dimerization step.

Other zeolites with medium pores, ZSM-12, -23, etc. produce oligomerswith a low branching degree due to the “shape selectivity” phenomenon.This is such that the gasoline cut, without aromatics, has a low octanenumber whereas the diesel cut has a high cetane number. Examples of theuse of this type of material, for producing diesel fuel with a highcetane index, are provided in some recent patents of Mobil (U.S. Pat.No. 5,639,931; U.S. Pat. No. 5,780,703).

Amorphous acid materials (silico-aluminas), large pore zeolites, resinswith cationic exchange and supported acids (e.g. phosphoric acid), onthe other hand, produce oligomers with a high branching degree and adiesel cut with a low cetane number.

All acid carriers supported with Ni also belong to a special category.This metal in fact is capable of competing with the acid sites of thecarrier, reducing the isomerization reactions and forming oligomers witha low branching degree (JP 07309786), but at the same time favoringdimerization with respect to oligomerization to heavier products,creating products with a boiling point lower than that whichdistinguishes diesel cuts.

One example of a suitable olefin metathesis and oligomerization processuses modified ZSM-5 and ZSM-23, and is disclosed in PCT WO 93/06069.

Broken Hill has patented zeolites (ZSM-5, -11, -12) modified with >0.2%by weight of K, Na, Ca oxides (with respect to the weight of thecatalyst, intended as zeolite plus ligand) in combined FCC andoligomerization systems (U.S. Pat. No. 4,675,460). In all the examplesof the patent, the yield of the diesel fraction is lower than 28% byweight with respect to all the products obtained.

Neste OY has obtained products with a cetane number equal to 49 and ayield of the diesel fraction lower than 50% by weight in the presence ofZSM-5 doped with 0.01%-1% by weight of Ca (EP 0539126); or equal to 55and a yield in the diesel fraction of less than 58% by weight with ZSM-5doped with 1-3% by weight of Cr (WO 96/20988).

Eniricerche S.p.A. and Agip S.p.A. have disclosed (Italian PatentIT-1204005) an oligomerization process of light olefins carried out inthe presence of a zeolite structurally similar to ZSM-5,titaniumaluminumsilicalite (Al-TS-1), which allows mixtures of olefinsand aromatics having from 5 to 20 carbon atoms to be obtained, with aselectivity of over 87%.

By effecting the oligomerization reaction of olefins in the presence ofa titaniumaluminumsilicalite in certain ratios and with an extraframework titanium oxide content of zero or below certain values, andoperating at a high pressure, it is possible to obtain high yields ofproducts with a high cetane number, suitable as fuels for dieselengines, in which the aromatic hydrocarbons are either substantiallyabsent or present in a very limited quantity.

One representative process, starting from ethylene, involvesoligomerizing ethylene in the presence of synthetic zeolites containingsilicon, titanium and aluminum oxides, having a molar ratio SiO₂/Al₂O₃ranging from 100 to 300, preferably from 200 to 300, a molar ratioSiO₂/TiO₂ greater than 41, preferably equal to or greater than 46, and aextra framework titanium oxide content which is zero or less than 25% byweight, preferably zero or at the most less than 5%, with respect to thewhole titanium oxide present, at a temperature ranging from 180 to 300°C., preferably from 200 to 250° C., at a pressure greater than 40 atm,preferably ranging from 45 to 80 atm. and a WHSV space velocity equal toor greater than 1 h⁻¹, preferably ranging from 1.5 to 3 h⁻¹, in order toobtain a stream essentially consisting of oligomerized C₅-C₂₄hydrocarbons. The resulting stream can be distilled to separate a C₅₋₁₅fraction, if Jet-B type fuels are desired, or a C₈₋₁₆ fraction, ifJet-A, Jet A-1, or JP8-type fuels are desired. The oligomers can thenoptionally be isomerized and/or hydrogenated. A process of this type isdescribed, for example, in U.S. Pat. No. 7,678,954.

Additional conditions for oligomerizing ethylene include those describedin:

-   Zhang, et. al., “Oligomerization of Ethylene in a Slurry Reactor    using a Nickel/Sulfated Alumina Catalyst”, Ind. Eng. Chem. Res.,    1997, 36, 3433-3438-   U.S. Pat. No. 8,021,620-   U.S. Pat. No. 8,093,439

Distillation of Oligomers to Isolate Jet Fuel Range Hydrocarbons

The oligomers obtained by oligomerizing ethylene can be distilled, andproducts in the desired boiling point and/or molecular weight ranges canbe obtained.

The paraffinic, olefinic, cyclic and/or aromatic compounds obtained byreacting dimethyl ether over a zeolite catalyst can also be distilled,and products in the desired boiling point and/or molecular weight rangescan be obtained.

Conditions for distilling hydrocarbons are well known to those of skillin the art.

Optional Isomerization Conditions

Optionally, various fractions are isomerized. The isomerization productshave more branched paraffins, thus improving their pour, cloud andfreeze points. Isomerization processes are generally carried out at atemperature between 200° F. and 700° F., preferably 300° F. to 550° F.,with a liquid hourly space velocity between 0.1 and 2, preferablybetween 0.25 and 0.50. The hydrogen content is adjusted such that thehydrogen to hydrocarbon mole ratio is between 1:1 and 5:1. Catalystsuseful for isomerization are generally bifunctional catalysts comprisinga hydrogenation component (preferably selected from the Group VIIImetals of the Periodic Table of the Elements, and more preferablyselected from the group consisting of nickel, platinum, palladium andmixtures thereof) and an acid component. Examples of an acid componentuseful in the preferred isomerization catalyst include a crystallinezeolite, a halogenated alumina component, or a silica-alumina component.Such paraffin isomerization catalysts are well known in the art.

Optional Hydrotreatment Conditions

Optionally, but preferably, the product from the oligomerization step,the isomerization step, and/or the step following conversion of thedimethyl ether to products over a zeolite catalyst is hydrogenated. Thehydrogen can come from a separate hydrogen plant, can be derived fromsyngas, or can be made directly from methane and other lighthydrocarbons.

After hydrogenation, which typically is a mild hydrofinishing step, theresulting distillate fuel product is highly paraffinic. Hydrofinishingis done after isomerization. Hydrofinishing is well known in the art andcan be conducted at temperatures between about 190° C. to about 340° C.,pressures between about 400 psig to about 3000 psig, space velocities(LHSV) between about 0.1 to about 20, and hydrogen recycle rates betweenabout 400 and 1500 SCF/bbl.

The hydrofinishing step is beneficial in preparing an acceptably stabledistillate fuels. Distillate fuels that do not receive thehydrofinishing step may be unstable in air and light due to olefinpolymerization. To counter this, they may require higher than typicallevels of stability additives and antioxidants.

Jet Fuel Compositions

In one embodiment, the invention relates to compositions, including jetfuel compositions, and compositions comprising components of jet fuelthat can be blended with other components to produce jet fuel.

In one aspect of this embodiment, a jet fuel composition is provided inaccordance with any of the processes described herein. Other variationsprovide per se novel jet fuel compositions, regardless of the processused to produce those compositions.

In one aspect of this embodiment, the compositions are capable ofburning in a jet engine without need for being blended with conventionaljet fuel. In another aspect of this embodiment, the compositions areblended with jet fuel, at concentrations between around 1 and around 99%by volume, around 10 and around 90% by volume, around 20 and around 80%by volume, around 30 and around 70% by volume, around 40 and around 60%by volume, and around 50% by volume. In this context, “around” meanswithin 4%.

The various fractions obtained by distilling the products of thedimethyl ether conversion and the ethylene oligomerization (as well asoligomerization of olefins resulting from the dehydration of higheralcohols) can be combined. The combined products include hydrocarbonsand aromatics in the jet fuel range. The exact combination of theproducts can vary, depending on the catalysts and conditions used toprovide the various components, and the desired type of jet fuel to beproduced.

The most commonly used fuels for commercial aviation are Jet A and JetA-1 which are produced to a standardized international specification.The only other jet fuel commonly used in civilian turbine-engine poweredaviation is Jet B which is used for its enhanced cold-weatherperformance. JP-8 is the jet fuel commonly used by the military.

Jet fuel is a mixture of a large number of different hydrocarbons. Therange of their sizes (molecular weights or carbon numbers) is restrictedby the requirements for the product, for example, the freezing point orsmoke point. Kerosene-type jet fuel (including Jet A and Jet A-1) has acarbon number distribution between about 8 and 16 carbon numbers;wide-cut or naphtha-type jet fuel (including Jet B), between about 5 and15 carbon numbers.

Differences Between Jet A and Jet A-1

Jet A specification fuel has been used in the United States since the1950s, whereas Jet A-1 is the standard specification fuel used in therest of the world. Both Jet A and Jet A-1 have a flash point higher than38° C. (100° F.), with an autoignition temperature of 210° C. (410° F.).

The primary differences between Jet A and Jet A-1 are the higherfreezing point of Jet A (−40° C. vs −47° C. for Jet A-1), and that JetA-1 typically includes an anti-static additive.

Typical Physical Properties for Jet a and Jet A-1

Jet A-1 Fuel must meet the specification for DEF STAN 91-91 (Jet A-1),ASTM specification D1655 (Jet A-1) and IATA Guidance Material (KerosineType), NATO Code F-35.

Jet A Fuel must reach ASTM specification D1655 (Jet A) [5]

Typical physical properties for Jet A/Jet A-1 fuel:

Jet A-1 Jet A Flash point 42° C. 51.1° C. Autoignition temperature 210°C. 210° C. Freezing point −47° C. −40° C. Open air burning temperatures260-315° C. 260-315° C. Density at 15° C. 0.804 kg/L 0.820 kg/L Specificenergy 43.15 MJ/kg 43.02 MJ/kg Energy density 34.7 MJ/L 35.3 MJ/L

Jet B

Jet B is a fuel in the naphtha-kerosene region that is used for itsenhanced cold-weather performance A blend of approximately 30% keroseneand 70% gasoline, it is known as wide-cut fuel. It has a very lowfreezing point of −60 degrees Celsius and a low flash point as well. Itis primarily used in US and some military aircraft.

Military Jet Fuel

Military organizations around the world use a different classificationsystem of JP numbers. Some are almost identical to their civiliancounterparts and differ only by the amounts of a few additives; Jet A-1is similar to JP-8, Jet B is similar to JP-4. Other military fuels arehighly specialized products and are developed for very specificapplications. JP-5 fuel is fairly common, and was introduced to reducethe risk of fire on aircraft carriers (JP-5 has a higher flash point—aminimum of 60° C.). Other fuels were specific to one type of aircraft.JP-6 was developed specifically for the XB-70 Valkyrie and JP-7 for theSR-71 Blackbird. Both these fuels were engineered to have a high flashpoint to better cope with the heat and stresses of high speed supersonicflight. One aircraft-specific jet fuel still in use by the United StatesAir Force is JPTS, which was developed in 1956 for the Lockheed U-2 spyplane.

Jet fuels are sometimes classified as kerosene or naphtha-type.Kerosene-type fuels include Jet A, Jet A-1, JP-5 and JP-8. Naphtha-typejet fuels, sometimes referred to as “wide-cut” jet fuel, include Jet Band JP-4.

JP-8, or JP8 (for “Jet Propellant 8”) is a jet fuel, specified and usedwidely by the US military. It is specified by MIL-DTL-83133 and BritishDefence Standard 91-87, and similar to commercial aviation's Jet-A.

JP-8+100 (F-37) is a version of JP-8 with an additive that increases itsthermal stability by 56° C. (a difference of 100° F.). The additive is acombination of a surfactant, metal deactivator, and an antioxidant.

Additives

The DEF STAN 91-91 (UK) and ASTM D1655 (international) specificationsallow for certain additives to be added to jet fuel, including:

Antioxidants to prevent gumming, usually based on alkylated phenols,e.g., AO-30, AO-31, or AO-37;

Antistatic agents, to dissipate static electricity and prevent sparking;Stadis 450, with dinonylnaphthylsulfonic acid (DINNSA) as the activeingredient, is an example

Corrosion inhibitors, e.g., DCI-4A used for civilian and military fuels,and DCI-6A used for military fuels;

Fuel System Icing Inhibitor (FSII) agents, e.g., Di-EGME; FSII is oftenmixed at the point-of-sale so that users with heated fuel lines do nothave to pay the extra expense.

Biocides are to remediate microbial (i.e., bacterial and fungal) growthpresent in aircraft fuel systems. Currently, two biocides are approvedfor use by most aircraft and turbine engine original equipmentmanufacturers (OEMs); Kathon FP1.5 Microbiocide and Biobor JF.

Metal deactivator can be added to remediate the deleterious effects oftrace metals on the thermal stability of the fuel. The one allowableadditive is N,N′-disalicylidene 1,2-propanediamine.

Additional additives include jet fuel ignition improvers, jet fuelstability improvers, jet fuel corrosion inhibitors, jet fuel detergentadditives, jet fuel cold flow improvers, jet fuel combustion improvers,jet fuel luminosity (particulate) reducers/radiation quenchers, jet fuelantimicrobial/antifungal adjuncts, jet fuel antistats, jet fuel smokemitigators, other conventional jet fuel adjuncts and mixtures thereof.

Such additives are known in the fuel-making art, see for example KirkOthmer, Encyclopedia of Chemical Technology, Wiley, N.Y., 4th Ed., Vol.3, pp. 788-812 (1992) and Vol. 12, pp. 373-388 (1994) and referencestherein. Percentages and proportions can be adjusted within ranges wellknown to formulators.

Types of Reactors Used in the Processes Described Herein

Reactors for conversion of one or more alcohols to jet fuel componentsare any type of reactor suitable for carrying out alcohol-to-jet fuelchemistry described herein. Preferably, the reactors include one or morezeolite catalysts effective for conversion of alcohols to jet fuelcomponents.

A “reactor” described herein may be any type of catalytic reactorsuitable for the conversion of syngas to alcohol mixtures. A reactormay, for example, be any suitable fixed-bed reactor. In some variations,a reactor comprises tubes filled with one or more catalysts. Syngaspassing through the tubes undergoes catalyzed reactions to form alcoholsor other products.

The reactor for converting syngas into alcohols can be engineered andoperated in a wide variety of ways. The reactor operation can becontinuous, semicontinuous, or batch. Operation that is substantiallycontinuous and at steady state is preferable. The flow pattern can besubstantially plug flow, substantially well-mixed, or a flow patternbetween these extremes. The flow direction can be vertical-upflow,vertical-downflow, or horizontal. A vertical configuration can bepreferable.

Any “reactor” used herein can in fact be a series or network of severalreactors in various arrangements. For example, in some variations, thereactor comprises a large number of tubes filled with one or morecatalysts.

The catalyst phase can be a packed bed or a fluidized bed. The catalystparticles can be sized and configured such that the chemistry is, insome embodiments, mass-transfer-limited or kinetically limited. Thecatalyst can take the form of a powder, pellets, granules, beads,extrudates, and so on. When a catalyst support is optionally employed,the support may assume any physical form such as pellets, spheres,monolithic channels, etc. The supports may be coprecipitated with activemetal species; or the support may be treated with the catalytic metalspecies and then used as is or formed into the aforementioned shapes; orthe support may be formed into the aforementioned shapes and thentreated with the catalytic species.

Reactors can consist of a simple vessel or tank, which can be stirred orunstirred. Preferably, reactors are closed reaction vessels, to preventloss of chemicals to the atmosphere. The reactions may be conductedbatch-wise, continuously, or semi-continuously.

The reaction temperature, pressure, and residence time for each processstep are each not regarded as critical, provided that overall conditionsare suitable for a desired conversion.

In general, solid, liquid, and gas streams produced or existing withinthe process can be independently passed to subsequent steps orremoved/purged from the process at any point. Also, any of the streamsor materials present may be subjected to additional processing,including heat addition or removal, mass addition or removal, mixing,various measurements and sampling, and so forth.

In some embodiments, the process is controlled or adjusted to attaincertain jet fuel properties. As is known, relevant jet fuel propertiescan include freezing point, flash point, energy content, water content,sediment content, ash content, sulfur content, nitrogen content,phosphorus content, pH, density, viscosity, and so on.

It can be difficult to obtain sufficient biomass to carry out thechemistry using a conventional reactor. In one embodiment, one or moreof the process steps is carried out using a micro-fluidic reactor ormicrochannel reactor. The reactor can include a heat exchanger, whichcan include a plurality of heat exchange channels adjacent to theprocess microchannels. In one embodiment, the heat exchange channels aremicrochannels.

In one aspect of this embodiment, the microchannel reactor includes atleast one process microchannel, the process microchannel having anentrance and an exit; and at least one heat exchange zone adjacent tothe process microchannel, the heat exchange zone comprising a pluralityof heat exchange channels. The heat exchange channels can extendlengthwise at right angles relative to the lengthwise direction of theprocess microchannels. The heat exchange zones can extend lengthwise inthe same direction as the process microchannels, and can be positionednear the process microchannel entrance. The length of the heat exchangezone is ideally less than the length of the process microchannel. Thewidth of the process microchannel at or near the process microchannelexit is ideally greater than the width of the process microchannel at ornear the process microchannel entrance. In one embodiment, the at leastone heat exchange zone includes a first heat exchange zone and a secondheat exchange zone, where the length of the second heat exchange zonebeing less than the length of the first heat exchange zone.

In one aspect of this embodiment, the process microchannels arecharacterized by having a bulk flow path. The term “bulk flow path”refers to an open path (contiguous bulk flow region) within the processmicrochannels. A contiguous bulk flow region allows rapid fluid flowthrough the microchannels without large pressure drops. The flow offluid in the bulk flow region can be laminar. Bulk flow regions withineach process microchannel can have a cross-sectional area of about 0.05to about 10,000 mm², and in one embodiment, about 0.05 to about 5000mm², and in another embodiment, about 0.1 to about 2500 mm². The bulkflow regions can include from about 5% to about 95%, and in oneembodiment, include from about 30% to about 80%, of the cross-section ofthe process microchannels.

The contact time of the reactants with the catalyst within the processmicrochannels typically ranges up to about 2000 milliseconds (ms), andin one embodiment, from about 10 ms to about 1000 ms, and in anotherembodiment, from about 20 ms to about 500 ms. In one embodiment, thecontact time may range up to about 300 ms, and in another embodiment,from about 20 to about 300 ms, and in a further embodiment from about 50to about 150 ms.

The space velocity (or gas hourly space velocity (GHSV)) for the flow ofthe reactant composition and product through the process microchannelsis typically at least about 1000 hr⁻¹ (normal liters of feed/hour/literof volume within the process microchannels) or at least about 800 mlfeed/(g catalyst) (hr). The space velocity typically ranges from about1000 to about 1,000,000 hr⁻¹, or from about 800 to about 800,000 mlfeed/(g catalyst) (hr). In one embodiment, the space velocity rangesfrom about 10,000 to about 100,000 hr⁻¹, or about 8,000 to about 80,000ml feed/(g catalyst) (hr).

The temperature of the reactant composition entering the processmicrochannels typically ranges from about 150° C. to about 400° C., andin one embodiment is between about 180° C. to about 350° C., and inanother embodiment, is from about 180° C. to about 325° C.

The temperature of the reactant composition and product within theprocess microchannels may range from about 200° C. to about 400° C., andin one embodiment is from about 220° C. to about 370° C.

The temperature of the product exiting the process microchannelstypically ranges from about 200° C. to about 400° C., and in oneembodiment is from about 320° C. to about 370° C.

The pressure within the process microchannels is typically between about5 and 50 atmospheres, more typically, 10 to about 50 atmospheres, and inone embodiment from about 10 to about 30 atmospheres, and in oneembodiment from about 10 to about 25 atmospheres, and in one embodimentfrom about 15 to about 25 atmospheres.

The pressure drop of the reactants and/or products as they flow throughthe process microchannels can range up to about 10 atmospheres per meterof length of the process microchannel (atm/m), and in one embodiment, upto about 5 atm/m, and in one embodiment up to about 3 atm/m.

The reactant composition entering the process microchannels is typicallyin the form of a vapor, while the product exiting the processmicrochannels may be in the form of a vapor, a liquid, or a mixture ofvapor and liquid. The Reynolds Number for the flow of vapor through theprocess microchannels is typically in the range of about 10 to about4000, and in one embodiment about 100 to about 2000. The Reynolds Numberfor the flow of liquid through the process microchannels is typicallyabout 10 to about 4000, and in one embodiment about 100 to about 2000.

The heat exchange fluid entering the heat exchange channels may be at atemperature of about 150° C. to about 400° C., and in one embodimentabout 150° C. to about 370° C. The heat exchange fluid exiting the heatexchange channels may be at a temperature in the range of about 220° C.to about 370° C., and in one embodiment about 230° C. to about 350° C.The residence time of the heat exchange fluid in the heat exchangechannels typically ranges from about 50 to about 5000 ms, and in oneembodiment, about 100 to about 1000 ms. The pressure drop for the heatexchange fluid as it flows through the heat exchange channels may rangeup to about 10 atm/m, and in one embodiment from about 1 to about 10atm/m, and in one embodiment from about 2 to about 5 atm/m. The heatexchange fluid may be in the form of a vapor, a liquid, or a mixture ofvapor and liquid. The Reynolds Number for the flow of vapor through theheat exchange channels is typically from about 10 to about 4000, and inone embodiment about 100 to about 2000. The Reynolds Number for the flowof liquid through heat exchange channels may be from about 10 to about4000, and in one embodiment about 100 to about 2000.

The conversion of dimethyl ether to products is ideally at least about40% or higher per cycle, and in one embodiment about 50% or higher, andin one embodiment about 55% or higher, and in one embodiment about 60%or higher, and in one embodiment about 65% or higher, and in oneembodiment about 70% or higher. The term “cycle” is used herein to referto a single pass of the reactants through the process microchannels.

The yield of products is ideally about 25% or higher per cycle, and inone embodiment about 30% or higher, and in one embodiment about 40% orhigher per cycle.

Using the microchannel reactors described herein, one can efficientlycontrol the heat generated from one or more of the exothermicmethanol-to-gasoline, methanol-to-olefin, and olefin oligomerizationreactions. Ideally, using the microfluidic approach, it may be possibleto carry out the entire synthesis, and only isolate products, such asunreacted syngas, methanol, dimethyl ether, and/or the products of thedimethyl ether-to-gasoline chemistry, as the products exit themicrochannel reactor.

All patents and publications disclosed herein are hereby incorporated byreference in their entirety and for all purposes. Modifications andvariations of the present invention, related to an alternative fuelcomposition, and blends of the alternative fuel composition withgasoline, will be obvious to those skilled in the art from the foregoingdetailed description of the invention. Jet fuel and other fuels areexpected to become a part of this patent, along with mixed alcoholsproduced using a molybdenum sulfide catalyst.

The present invention has utility with respect to biorefinery concepts.Final product mixes from a biorefinery can be optimized for maximumprofitability and/or minimum carbon footprint, for example, by knowntechniques. Preferred embodiments of the invention can reduce overallenergy intensity and/or reduce the number of processing steps tomanufacture renewable jet fuel.

All publications, patents, and patent applications cited in thisspecification are incorporated herein by reference in their entirety asif each publication, patent, or patent application was specifically andindividually put forth herein. All ASTM specifications recited hereinare also incorporated by reference.

In this detailed description, reference has been made to multipleembodiments of the invention and non-limiting examples relating to howthe invention can be understood and practiced. Other embodiments that donot provide all of the features and advantages set forth herein may beutilized, without departing from the spirit and scope of the presentinvention. This invention incorporates routine experimentation andoptimization of the methods and systems described herein. Suchmodifications and variations are considered to be within the scope ofthe invention defined by the claims.

Where methods and steps described above indicate certain eventsoccurring in certain order, those of ordinary skill in the art willrecognize that the ordering of certain steps may be modified and thatsuch modifications are in accordance with the variations of theinvention. Additionally, certain of the steps may be performedconcurrently in a parallel process when possible, as well as performedsequentially.

Therefore, to the extent that there are variations of the invention,which are within the spirit of the disclosure or equivalent to theinventions found in the appended claims, it is the intent that thispatent will cover those variations as well. The present invention shallonly be limited by what is claimed.

The invention claimed is:
 1. A process for producing a mixturecomprising aromatics and hydrocarbons in the C₅₋₁₅ range, comprising:(a) generating or providing syngas by gasifying a feedstock selectedfrom the group consisting of coal, methane, glycerol, biomass, blackliquor, municipal solid waste, and lignin; (b) converting the syngas tomethanol over an appropriate methanol-synthesis catalyst; (c) separatingthe methanol into at least a first stream and a second stream; (d)converting the methanol in the first stream to dimethyl ether; (e)reacting the dimethyl ether with ZSM-5 or H-ZSM-5 to one or more jetfuel range hydrocarbons and aromatics; (f) converting the methanol inthe second stream to olefins using a methanol-to-olefins catalyst; (g)oligomerizing the olefins under conditions which produce olefins in thejet fuel range; (h) isomerizing and hydrotreating the olefins in the jetfuel range formed during the olefin oligomerization step to formparaffins in the jet fuel range; (i) isolating products in the jet fuelrange obtained from step (h), and combining said isolated products withthe one or more jet fuel range hydrocarbons and aromatics from step (e)to provide a mixture comprising aromatics and hydrocarbons in the C₅₋₁₅range; and (j) blending said mixture comprising aromatics andhydrocarbons in the C₅₋₁₅ range as a blendstock with JP8, JPA, JP4, orJP1.
 2. The process of claim 1, wherein said syngas is derived frombiomass.
 3. The process of claim 1, wherein said syngas is derived fromcoal.
 4. The process of claim 1, wherein said syngas is derived frommethane.